IMMUNE MYOPATHY WITH ANTIBODIES TO SIGNAL RECOGNITION PARTICLE

EARLY PATHOLOGY H&E stain Scattered degenerating & regenerating fibers	NADH stain Coarse internal architecture in muscle fibers
Acid phosphatase stain Scattered necrotic muscle fiber	Alkaline phosphatase stain Alkaline phosphatase stains an increased number   of endomysial vessels (Arrow)

INTERMEDIATE PATHOLOGY H&E stain Bimodal muscle fiber sizes	Acid phosphatase stain Scattered necrotic muscle fiber	Acid phosphatase stain Acid phosphatase positive cells in endomysium

LATE PATHOLOGY: Months H&E stain Increased endomysial connective tissue Hypertrophic and small muscle fibers	Gomori trichrome stain Many small rounded muscle fibers Increased endomysial connective tissue	H&E stain Marked increase in endomysial connective tissue Disease course of only 6 months

CAPILLARY PATHOLOGY Ulex europaeus agglutinin I stain Normal muscle: Small endomysial capillaries	Ulex europaeus agglutinin I stain SRP myopathy: Enlarged endomysial capillaries
Ulex europaeus agglutinin I stain SRP myopathy: Endomysial capillaries are enlarged & reduced in number

MEMBRANE ATTACK COMPLEX: C5b-9 IN CAPILLARIES
Antibody vs C5b-9 C5b-9 Deposition in endomysial capillaries   and necrotic muscle fiber cytoplasm (Arrow)	Antibody vs C5b-9 C5b-9 Irregular deposition in endomysial capillaries (Arrows)